Preston et al. U.S. Pat. No. 3,225,011 teaches the preparation of poly-p-aminobenzoic acid by a slurry polymerization technique in which a proton acceptor is employed. Kwolek U.S. Pat. No. 3,600,350 teaches the solution preparation of poly(1,4-benzamide) and copolymers of poly(1,4-benzamide) wherein up to 20 mole percent of copolymeric units may be derived from halogen-substituted derivatives of 4-aminobenzoyl chloride hydrochloride, e.g., 2-chloro-4-aminobenzoyl chloride hydrochloride.
Caldwell et al. U.S. Pat. No. 3,408,334 teaches the preparation of polyamides by condensing aromatic amino acids in the presence of a catalytic amount of a tin compound. Jones U.S. Pat. No. 3,753,957 teaches preparation of aromatic polyamides by condensing an aromatic ester of an aromatic amino acid to an oligomer which is then polymerized to a high viscosity product.